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Configuring Ethernet link aggregation
Ethernet link aggregation bundles multiple physical Ethernet links into one logical link, called an
aggregate link. Link aggregation has the following benefits:
•
Increased bandwidth beyond the limits of any single link. In an aggregate link, traffic is
distributed across the member ports.
•
Improved link reliability. The member ports dynamically back up one another. When a member
port fails, its traffic is automatically switched to other member ports.
As shown in
, Device A and Device B are connected by three physical Ethernet links. These
physical Ethernet links are combined into an aggregate link called link aggregation 1. The bandwidth
of this aggregate link can reach up to the total bandwidth of the three physical Ethernet links. At the
same time, the three Ethernet links back up one another. When a physical Ethernet link fails, the
traffic previously carried on the failed link is switched to the other two links.
Figure 8 Ethernet link aggregation diagram
Basic concepts
Aggregation group, member port, and aggregate interface
Link bundling is implemented through interface bundling. An aggregation group is a group of
Ethernet interfaces bundled together, which are called member ports of the aggregation group. For
each aggregation group, a logical interface (called an aggregate interface), is created. When an
upper layer entity uses the link aggregation service, the following events occur:
•
A link aggregation group appears the same as a single logical link.
•
An aggregate interface transmits data traffic.
When you create an aggregate interface, the device automatically creates an aggregation group of
the same type and number as the aggregate interface. For example, when you create aggregate
interface 1, aggregation group 1 is created.
You can assign Layer 2 Ethernet interfaces only to a Layer 2 aggregation group.
The port rate of an aggregate interface equals the total rate of its Selected member ports. Its duplex
mode is the same as that of the Selected member ports. For more information about the states of
member ports in an aggregation group, see "
Aggregation states of member ports in an aggregation
."
Aggregation states of member ports in an aggregation group
A member port in an aggregation group can be in any of the following aggregation states:
•
Selected
—A Selected port can forward traffic.
•
Unselected
—An Unselected port cannot forward traffic.
•
Individual
—An Individual port can forward traffic as a normal physical port. A port is placed in
the Individual state when the following conditions are met:
{
The corresponding aggregate interface is configured as an edge aggregate interface.
